Cal. PUC § 767

Whenever the commission, after a hearing had upon its own motion or upon complaint of a public utility affected, finds that public convenience and necessity require the use by one public utility of all or any part of the conduits, subways, tracks, wires, poles, pipes, or other equipment, on, over, or under any street or highway, and belonging to another public utility, and that such use will not result in irreparable injury to the owner or other users of such property or equipment or in any substantial detriment to the service, and that such public utilities have failed to agree upon such use or the terms and conditions or compensation therefor, the commission may by order direct that such use be permitted, and prescribe a reasonable compensation and reasonable terms and conditions for the joint use. If such use is directed, the public utility to whom the use is permitted shall be liable to the owner or other users for such damage as may result therefrom to the property of the owner or other users thereof, and the commission may ascertain and direct the payment, prior to such use, of fair and just compensation for damage suffered, if any.